The role of hypothalamic biogenic amines in the "gonadostat theory of puberty" is being examined by: 1) characterizing the alterations that occur in hypothalamic biogenic amine content and turnover during normal sexual maturation in male and female rats; 2) determining the effect of gonadal secretions on these parameters by repeating biogenic amine measurements in castrated animals of similar ages; and 3) testing the hypothesis that changing sensitivity of the hypothalamic-pituitary axis to the negative feedback effects of gonadal steroids is mediated through changes in hypothalamic neurotransmitter metabolism. Intact and castrated male and female rats are sacrificed at various ages during sexual maturation. Other groups of male and female rats are castrated and implanted with silastic capsules containing four increasing doses of testosterone or estradiol respectively. After seven days, these animals are being sacrificed. Serum is obtained from all animals for the determination of LH, FSH, estradiol and/or testosterone (by RIA). Brains are removed for measurement of norepinephrine and dopamine content (by I125 RIA), NE turnover (by the alpha methyl-p-tyrosine synthesis inhibition technique). The biogenic amine measurements are being performed in four subdivisions of the hypothalamus: ventral anterior hypothalamus, dorsal anterior hypothalamus, medial basal hypothalamus and residual hypothalamus. By this approach, the complex relationships between gonadal steroids, biogenic amine metabolism in specific hypothalamic areas and pituitary gonadotropin secretion during sexual maturation can be defined and insight gained into the role of these systems in the process of puberty.